Nickel-chromium alloy

ABSTRACT

A NICKEL ALLOY CONTAINING 30 TO 35 WEIGHT PERCENT CHROMIUM AND 3.5 TO 3.9 WEIGHT PERCENT SILICON WITH SMALL AMOUNTS OF CARBON, TITANIUM AND MANGANESE IS HIGHLY CORROSION RESISTANT TO HOT, LIQUID AND VAPOR PHASE NITRIC ACID SOLUTIONS, CONTAINING IRON (III), CHROMIUM (VI) AND FLUORIDE IONS.

United States Patent I 311,514,612

Patented Apr. 13, 1971 SUMMARY OF THE IN ENTION EL idiim ALLOY V NICK. 'CHRO This invention comprises a nickel alloy containing about g z gg ifi gg g g gggzgg fig zgz ig z gzg ig 30 to 35 percent by weight of chromium, where the nickel Atomic Energy Commission and chromium combined total about 94 to 96.5 percent No Drawing. Filed Feb. 3, 1969, Ser. No. 796,176 by weight, with about 3.2 to 4.2 percent by weight of n 322 19 00 SlllCOl'l, an effective amount up to about 3 percent by U.S. Cl. 75--171 2 Claims weight of titanium and manganese and less than 0.02 percent by weight of carbon.

ABSTRACT OF THE DISCLOSURE 1O DETAILED DESCRIPTION OF THE PREFERRED A nickel alloy containing 30 to 35 weight percent EMBODIMENT chromium and to f l Percent Silicon wit}: A number of alloys were tested to measure their reamoun.ts of F manulm manganese 1S sistance to corrosion by a variety of nitric acid solutions. l l P P reslstantf? q hquld and vallor phase Some tests were also conducted with 304L stainless steel mtnc So1.u Hons contammg Iron (111) chromlum (VI) to provide a standard for comparison. Because the welds and fluoride Ions in reprocessing equipment are often the weakest part of the equipment, some of the tested samples were heated to simulate the heating conditions during welding. These CONTRACTURAL ORIGIN OF THE INVENTION The invention described herein was made in the course Samples ,referred to in the data as sensitized and of, or under, a contract with the United States Atomic were mamtamed at a temperature of 12500 f one Energy commission hour andhthen watelrl quercliledivlazcausel glloride ionhappears in e vaporp ase o t e an evaporp ase BACKGROUND OF THE INVENTION may be more corrosive than the liquid phase, tests were This invention relates to a corrosion resistant alloy and conducted to determine corrosion due to both liquid and in particular to a nickel-chromium alloy resistant to hot vapor phases. In the tests and tables contained herein, nitric acid Solutions containing iron Chromium alloy number 1 is the subject matter of this invention.

and fill ridoimls. The results of the tests are reported in the following Reprocessing of irradiated nuclear fuels may require tables;

extremely corrosive liquids in order to dissolve both the cladding material and the fuel. Waste solutions produced from reprocessing are often concentrated by evaporation prior to storage and/or disposal, and these waste solutions TABLE I' NOMINAL fi flfi fg OF EXPERIMENTAL as well as the reagents used for fuel assembly dissolution are so corrosive that the service life of ordinary alloys is Weight percent relatively short. The so-called Purex process uses nitric Fe Ni CY M0 011 Ti Si Mn 0 acid in the separation of uranium, plutonium and fission A110yN0 products and produces a waste stream, hereinafter IWW, 61 34 61 30 4.0 1.0 3.7 0.6 0. 02 with the following approximate composition: 20 18 M Q02 25 6.0 1.0 1.0 3.7 0.6 0. 02 6M HNO 0.4M NaNO 0.4M H 50 0.3M Fe (SO 50 25 6.0 1.0 3.7 0.6 0.02

0.01M Na PO 0.01M CrO 0.01M Hg(NO TABLE IL-CORROSION RATES IN NITRIC ACID SOLUTIONS A. Five 48-hour exposures 1 B. Five 48-hour exposures 2 0. Five 48-hour exposures 3 Corrosion rate, mils/month period Corrosion rate, mils/month period Corrosion rate, mils/month period Aver- Aver- Aver- 2 3 4 5 age 1 2 3 4 5 age 1 2 3 4 5 age 0. 37 0. 34 0. 25 0. 38 0. 35 0. 71 O. 50 0. 39 0. 30 0. 32 O. 44 0. 22 0. 25 0. 18 0. 17 0. l4 0. 19 0. 85 O. 0. 95 0. 84 0. 86 1. 52 1. l8 0. 93 0. 93 0. 98 10 0 98 0. 0. 70 0. 67 O. 67 O. 74 2. 74 2. 70 3. 21 3. 20 3. 05 3. 34 4. 33 3. 56 5. 39 5. 4. 50 2. 23 2. 09 2. 84 3. 67 4. 43 3. 05 1. 78 1 84 2. 09 2. 13 1. 96 2. 05 2. 68 3. 25 4. 59 5. 41 3. 59 2. 08 2. 19 2. 74 3. 87 3. 40 2. 86 2. 39 2. 52 3. 04 3. 15 2. 74 1. 77 1. 69 1. 87 2. 54 2. 81 2. 14 1. 60 1. 50 1. 53 1. 86 1. 94 1. 69

1 To boiling 65 w/o nitric acid. Corrosion Specimens in annealed condition. 2 To boiling 65 w/o nitric acid. Corrosion specimens in sensitized condition. 3 To boiling 60 w/o nitric acid. Corrosion specimens in sensitlzed condition.

Due to changes in the type of cladding material as well TABLE IQ Q g 'lgg g SILUMATED PUREX as operating condnilons. m the Purex, q the 1W [Conditionsz Five 48-hour exposures to boiling solutions. Sensitized now contains fluoride ion. The fluoride 1011 coacts with corrosion specimens] the iron (III) and chromium (VI) ions already present 60 in the IWW to promote acid corrosion of the process equipment. Because the fluorides are volatile they affect Alloy 1 2 3 4 5 Average the corrosiveness of not only the liquid phase but also the Corrosion rate, mils/month period I 1.35 1.63 1.77 2.30 1.69 vapor phase of the IWW. It ids, therefore, the principal 65 8:8; 3'22 122 kg;

t i ent'ont rovi na 0 resistant to aci -39 3- 6.39 .40 oblec 0ft smv 1 op ea y 1.62 2.18 2.84 2.06 1.03

corrosion by IWW solutions containing fluoride ion.

TABLE IV.CORROSION RATES IN PUREX IWW SOLUTION CONTAINING Alloy N 0.

all alloys except number 4 With reference to Tables IV, V and VI, various addi- 6 6 n S mmu m nwm .1 a t C .w e a sH O r. nvd a 6.1 .1 V t p h m C U H e 0 C e mfm umn e f S f V m e a e t .1. OJ mt m n .1. 6 n e n m m 2. wm umh n a e e mwl 6b 0 e a g r b u c a t C pe a S n m 61 s r t m 0 6 .T. d I a pp d 1 10 W S C 0 e r. k a m n a c d n 0 d 2 0 C T m 0 W a .1 O H Y .1 .E g 1% a 6 H21 3. m uhfl O u i v 1 t n r n n V 0 r L o. m A 0 m 0 e 6 0 a u 3M L H 9 W M gMfl P 1.. 5.1%.. mm m am1 r L 1 I u+ S5 0 w m n 9 o u w flmn m c S 0 0 4. n m f I 0 1 4 8 y 0b 0 m a. m M mm Mi s I L e n. 6 r 0 m r O m d 0 17113 8 7026 ha Ch 3 M 0 6 1500 m g I O n W d U G .m w 1883A m m 0 3. W d mg 4.60 nd e m m Wh 02 6 18 N .m M 00 2 5 2 W m we 2 1 m mm v 2272 .1 m m h m m N w 1 pie... X m 1 12.? I t e r. I .1 S tt 8 C d O 2 r h D O I s O f. 91754 A -M I 5 541 W P 3 E 0 3 5392 O 1 1 n C a 5 6.. d 1559 3 0 4. IX luvlennv 052mm m mm 0 0 403 H mm V 1 m m m m m H %& 0 e u a s1 a c 0 sm 0 N S0 fir 30 L H 5 O 5 swam. 0 m mm 4 mwmmm m mm m m mm 2 wwmn 5 e e o o... 28 N i m 0161.. P w 0 Z. 2 N .m mm 1227.. m M anm 0 a. 9 57034 0 .ID N 3 9854 G .1 W 32 6 I d D. 1 0906 .1 a .3 34604 H M mm 11089 N t m A 5 R M Wm 74036 1 W H 021 11 0 1 e 1 i 02693 Um .amem. 00132 m mm m 5 M Ms M m I 2192 M. gee no w 2 none.. A mm m BL m 2.... we. 2 N 0 0 3n N n 2 0 0 02 L E mx n .4 c m v we 8 S we V B 6 0d 4 5 4 E% S 5 A 3 2 Y E 48828 WA 0 1 23035 m mm D m MP 0 n 5 emwm %H H M W mm 1 .1 m m um. 52 1 mm d m. 3 85402 m wm 010 0 0 0 L 01336 I 01131 0 u n 3 .0 t IO 0U C 3 9 8 OZ 1 B 510 n 6 261 x0 P. P am N me am 0. on N am 232 1 1 mn 4 m m n N 17 7 D ot eg A 0 w e0 1 1 L g h/ 2 5 3 F n 0 2 0 1 0 L 04111 R M 1 M 01446 U m hm 2 9 fi n DB M M O 2 Z 3 1 e UA mm m H mm e A m mm 223 7 s mm 3 ..m%.% m m. n 30324 E 0 r 5 52340 m m 62 2 I b We 1 5892 ES .m 0.10. 01 0. L 5 0 ND nd 4040. N .me a 1 S o n 0494 TT .n 9212 11 M mm 0 3 7 1 m an m MN n L.. 4.30.7.5 N mm 2 man a N m 92358 SR m mm. 4 1027 m 11.8. 5.2. H T m RE Om 0 L Lwm 0 1 EU 58 T 53504 w It A U U N 11m 0 612P mm Mm 2 03 9 M "n "m U M. m OD W1 1 W H e 9 S n L S .4 RF m m a gnaw F. m L m Nu m "m N NE N2 121 12 1 04121 NW n w W 01333 N a u HW OS m m 1 W n 4 0 3 00 0. am 3423 m r I m m m .A R e amiss a as m 2 4110 s 1 1M" o n In 0 mm oasnz 0 mm m 0 1 2 2 2 0 m n "m m R 4 m n m 0 m 1732 R 1 1 211.... m w. 5 me 2 m :1 N 1 41583 R Mn 52208 0 e F w o F F .F FF Mm 5 l .1 41444 2 02545 now w 01222 C E Fm m HHHHH I m I F m F m N "m .1 m NNNNN v F 3 u .2 a or e I nn 3 n w v m m m w 1 M New v c MMMMM m N m s .l n n F m m n n F m m mem n n mmam B mm H mm m m m w y m m m m .1 W. m m mwwww m a. m M O u 11 u U I A 0 H A. 0 l V A A l V O l 1 5 T 1 A L s T w a nmm T m mmnmm m. m m

hibits corrosion of the number 1 alloy and, to this extent, Five 244101" expsuresis beneficial rather than harmful. Table VI shows that With reference to Table II, an average corrosion rate the presence of n+ ion reduces the corrosion rate of f about 2 mils per month or less is acceptable f isolutions 0.5 M in fluoride 1011 to acceptable values. tized samples contacted with a W/O nitric acid solution. With reference to Tables VII and VIII, both sensitized Table II shows that only alloys 1 and 2 (see Table I for 304L stainless steel and weldments of alloy number 1 their nominal compositions) are acceptable. were subjected to corrosive action of IWW with various- With reference to Table III, a simulated Purex IWW fluoride additions. The superior corrosion resistance of solution as hereinbefore defined was used throughout. alloy number 1 is clearly shown by comparison of the Corrosion was general over the sample tested with little ables. Additions of Cu+ ion, as shown in Table VIII, as

well as addition of Al+ ion permits high fluoride concentrations to be used with acceptable corrosion rates. It should be noted that rarely in alloy experiments one particular specimen will behave ditferently than other specimens of the same alloy. The fifth specimen in the 6 M NH F0.5 M NH NO experiment in Table VIII remained passive to the solution to a much greater degree than did the other four specimens.

The number 1 alloy has good forging and rolling char acteristics as a A; inch sheet was produced from a 15- pound ingot. Ductile welds were produced using the tungsten-inert gas technique and strips from the base metal as filler metal. Both titanium and manganese are present to give the abovementioned rolling and forging characteristics and do not, as far as known, materially improve resistance to corrosion. See also, the exact Weight percents of nickel and chromium are not critical within about 5 to 6 weight percent of the value specified in Table I for alloy number 1. The amount of silicon is considered critical within /5 to /2 of a weight percent of the value specified in Table I for alloy number 1.

The experiments cited herein are meant to be illustrative of the invention but not to define it. The invention is defined in the following claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as fel w 1. An alloy, for use in process equipment subjected to corrosion by solutions containing nitric acid and fluoride ions, consisting essentially of:

to percent by weight of chromium;

59.08 to 66.5 percent by Weight of nickel;

0 to 0.02 percent by weight of carbon;

an effective amount up to 0.8 percent by weight of manganese for workability;

an effective amount up to 1.2 percent by weight of titanium for workability; and

3.5 to 3.9 percent by weight of silicon.

2. The alloy of claim 1 wherein the chromium concentration is 34 percent by Weight, the nickel concentration is 61 percent by weight, the silicon concentration is 3.6 percent by weight, the titanium concentration is 0.90 percent by weight, the manganese concentration is 0.48 percent by weight and the carbon concentration is 0.02 percent by weight.

References Cited UNITED STATES PATENTS RICHARD O, DEAN, Primary Examiner 

